Endogenous bacterial endophthalmitis (EBE) is a devastating infection caused by the migration of organisms into the eye from a distant site of infection. Although antibiotic and surgical treatment of ocular bacterial infections has greatly improved over the past few decades, the visual outcome of EBE has not improved in the past ~50 years. Populations at greatest risk for EBE include immunocompromised patients (including diabetics) or those on immunotherapy, those with prolonged indwelling devices, and intravenous drug abusers. The potential for bilateral blindness makes EBE one of the most devastating and virulent ocular infections. A critical barrier to progress in improving the clinical outcome of EB is a lack of knowledge about the pathogenic mechanisms of disease. This important goal could be achieved through studies in experimental models of EBE; however, no such EBE model currently exists. The mechanisms of bacterial migration into the eye from the bloodstream are not well understood. Our research seeks to fill that existing information gap by developing and characterizing new models of EBE. K. pneumoniae and S. aureus are opportunistic pathogens that cause a variety of infections and are the most common etiologic agents of EBE. An increasing number of K. pneumoniae and S. aureus EBE cases are being reported, specifically in diabetic patients. This R21 proposal seeks to develop and characterize new experimental models of K. pneumoniae and S. aureus infection in mice. These models will incorporate a streptozotocin-induced diabetic mouse model to analyze the contribution of the diabetes to the spread of infection from the bloodstream into the eye. Based on preliminary data demonstrating a greater incidence of EBE in diabetic mice with greater blood-retinal barrier permeability, we hypothesize that that the diabetic ocular environment facilitates migration of bacteria into the eye, causing EBE. However, because diabetes causes a number of systemic and local changes that might contribute to EBE development, questions remain as to which aspect of the diabetic ocular environment is most important. Development of well- characterized EBE models will allow us to address those questions. The proposed studies are a logical outgrowth of our long-standing endophthalmitis research program, and we are well positioned to contribute new and valuable information that will advance our long range goal of developing a detailed understanding of the specific factors (bacterial and host) that contribute to bacterial migration toward and into the eye and ocular damage and inflammation during EBE. Our findings will positively impact the ocular infectious disease field by introducing new infection models that can ultimately be used to test therapeutics in an effort to improve the clinical outcome of this blindig disease.